The present invention is directed to devices that are used to harvest fruit and nuts from trees, and, more particularly to a method and apparatus, when combined with a mechanical tree shaker, to harvest fruit and nuts from trees without damaging the bark of the tree and causing injury to the tree.
Mechanical tree shakers are well known for harvesting fruit and nuts from trees. Typically, mechanical tree shakers employ a clamping mechanism which grasps the tree trunk or branches with padded jaws and vigorously shakes the tree to dislodge the fruit or nuts, allowing these food products to be easily picked up off of the ground or from a collection device. A disadvantage of harvesting trees with mechanical tree shakers is that the clamping mechanisms have been known to damage trees by abrading, stripping, gouging or peeling away the tree bark and causing injury and death to the cambium layer of cells beneath the bark during the tree shaking process. The thin cambium is a living tissue that is responsible for producing bark and wood. The cambium layer is often injured and reinjured by the powerful mechanical shakers used to harvest tree crops. Damage to the bark and death of the cambium layer can reduce the productive life of a fruit or nut tree because rot-causing microorganisms infect the debarked wounds of the tree.
Previous devices have been suggested to protect trees from the injuries caused by mechanical shakers. These devices address the problem by padding the contact surface between the clamping mechanism and the tree bark. The simplest device is a solid rubber pad. However, because the surface of the tree engaged by the shaker clamp is not a uniform surface, the rubber pads will not make complete contact with the circumference of the tree, resulting in slippage or concentrated loading, both of which will injure the tree. Therefore, many devices use a deformable pad between the clamping mechanism and the tree bark to increase the surface area of the pad in contact with the tree.
As the clamping mechanism is tightened around the tree, these pads are deformed to provide uniform contact against the surface of the tree. However, various problems are associated with the deformable pads. If the filler material is too stiff, the pad surface will behave as a solid rubber pad and will not adequately conform to the surface of the tree, resulting in slippage, abrasion and injury to the tree. If the deformable pad is loosely packed with fill material, the fill material absorbs the vibratory force of the shaker before it reaches the tree, thereby reducing the efficiency of the shaker. The composition of the fill material is also important. It is known that during the shaking operation, the fill material can become extremely hot, such that the fill material melts, breaks down or results in gas buildup inside the pad.
A number of attempts have been made to resolve the difficulties associated with deformable pads. U.S. Pat. No. 3,318,629 discloses deformable engagement pads which are filled with a loose packing of granular material, such as sand, metal particles or plastic bits, which can conform to the shape of the tree trunk or limbs. U.S. Pat. No. 4,521,468, recognizing that previously proposed filler materials become overheated during the shaking process, proposes filling the contact pads with small rods of a high impact strength polymer impregnated with a dry, high-melting temperature lubricant. U.S. Pat. No. 5,406,780 discloses a compliant engagement member which resists deformation along the axis of vibration, but which allows off-axis deformation to prevent slippage against the tree. However, all of these inventions attempt to solve the problems associated with deformable pads by modifying the pad, rather than applying the shaking force to a less sensitive part of the tree.
The present invention is directed to an apparatus and method for mechanically shaking a tree without causing injury to the bark or the cambium layer. While this invention protects undamaged trees from initial injury, it also protects pre-existing wounds from reinjury, thereby allowing damaged trees to heal. While some other pad devices attempt to prevent injury by modifications to the pad, those devices nevertheless transfer the load from the mechanical shaker to the outside surface of the tree trunk through the intervening pad. However, the present trunk-pad transfers the shaking force directly from the mechanical shaker through the trunk-pad to the heartwood of the tree thereby circumventing the bark and cambium tissues.
The trunk-pad comprises an engagement member for connection to the clamping mechanism of a mechanical tree shaker and a longitudinal fastener which transfers the load imparted by the mechanical shaker at the engagement member to the inside of the tree. The engagement member, comprising an outside surface and an inside surface, is constructed so that it might be grasped within the clamping mechanism of the tree shaker. Protruding from the inside surface of the engagement member is a longitudinal fastener having a near end, attached to the engagement member, and a distal end which is adapted to penetrate into the heartwood of the tree trunk. When the disclosed invention is used for shaking a tree, two or more of the trunk-pads are installed on opposite sides of the trunk or limb of a tree, so that each engagement member is the point of contact between the clamping mechanism of the mechanical tree shaker and the tree. Once installed, the disclosed trunk-pad may be used repeatedly, but may also be removed as a tree grows.
In other embodiments of the present invention, a multiplicity of longitudinal fasteners are used on each trunk-pad, which may be used to attach the trunk-pad to trees with larger diameter trunks or where it is desirable to apply a greater shaking force to the trunk-pad. The multiple fasteners increase the load bearing surface of the fasteners thereby allowing greater shaking force to be applied to the tree.